Behavior of volatiles and ore-forming metals during high-pressure differentiation of arc magmas

• Applicant: Dr. Andreas Audétat
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520462435

Several studies have proposed that a critical factor in the formation and localization of ore deposits in the Earth's crust is the existence of a source region rich in ore metals, from where these metals are then transported to concentrate in orebodies finally. One of the potential metal-rich sources invoked, particularly concerning the formation of large auriferous provinces, is a metasomatized subcontinental lithospheric mantle (SCLM). Therefore, the main goal of this project is to understand the relationship between mantle metasomatism, the generation of fertile domains in the SCLM, and, ultimately, the formation of arc-related magmatic-hydrothermal ore deposits. In this scenario, Patagonia provides an ideal location to investigate mantle processes (e.g., partial melting, and metasomatism) affecting the SCLM near active subduction zones, as abundant ultramafic mantle xenoliths are found throughout the region. Moreover, several epithermal Au-Ag deposits are hosted in Jurassic volcanic rocks in the North Patagonian and Deseado massifs, two large massifs located in the south and north of Patagonia, respectively. However, these ore deposits seem to be more common in southern Patagonia, where recently, the presence of native gold in the SCLM beneath the Deseado massif, the world's southernmost metallogenic region, was reported. This apparent higher abundance of metals in the southern Massif compared to the North Patagonian Massif may reflect the geochemical differences of their respective SCLM. In this project, we will study the geochemistry of ultramafic xenoliths that sample the North Patagonian lithospheric mantle, with a particular focus on the concentration of their chalcophile elements Se and Te, in addition to their Se isotope signatures, to investigate depletion/enrichment processes recorded in the Patagonian SCLM and their links with the chalcophile metal-bearing systematics. Ultimately, this information will be combined with available data from southern Patagonian xenoliths to investigate possible links between their distinct mantle reservoirs and the formation of ore deposits in the crust.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2238: Dynamics of Ore-Metals Enrichment - DOME